MPEG is a compressed video signal protocol established by the Moving Pictures Experts Group of the International Standardization Organization. This protocol defines a versatile signal format which includes both intraframe coding and motion compensated predictive coding. Due to variations in coding format frame to frame, and variations in image content, different frames have widely divergent quantities of compressed data. As a consequence of different frames being compressed with different quantities of data etc., frames of data tend to be transmitted asynchronously.
Audio signals may also be compressed according to an MPEG protocol. Compressed audio may be associated with video but transmitted independently. For transmission the compressed audio is segmented into packets which are then time division multiplexed with the compressed video signal in a non synchronous manner.
Associated compressed audio and video components are not only independently asynchronous, but their mutual temporal relationships or synchronism is nonexistent in transmission.
MPEG compressed audio and video component signals may include presentation time stamps (PTS) to establish a reference between particular compressed signal segments and a system reference clock signal. The audio and video PTS's are utilized by receiver apparatus to both resynchronize respective decompressed components and to restore their temporal interrelationship.
A particularly annoying feature of reproduced A/V material is a loss of lip-sync which is the loss of synchronization between lip or mouth movement and the associated spoken word or audio. One of the objects of this invention is the elimination of annoyances of loss of lip-sync.